GRAPTOLITES OF NEW YORK, PART 2 305 



thecae subhorizontal in their direction, provided with short, frequently 

 curved lateral spines. Sicula relatively large (1.6 mm), frequently free 

 within the axil, with short, rigid, rodlike nema and inconspicuous virgella. 

 Thecae numbering 9 to n within 10 mm (23-30 in 1 inch), 10 being the 

 average number in the mature branches, overlapping one fourth their 

 length ; ventral margin of distal free part slightly convex ; apertural part 

 slightly introverted ; apertural excavation round, occupying about one third 

 the transverse width of the branch ; apertural notch obliquely reflected. 



Position and localities. D. gurleyi occurs not infrequently in the 

 Normanskill shale at Stockport, whence Gurley has described it ; at 

 Glenmont it is one of the most common, and by reason of its size and 

 numerous flexures and scrolls one of the most conspicuous of the grapto- 

 lites. It has also been observed in a few specimens at Mt Moreno. Its 

 associates at Glenmont are D i p 1 o g r . foliaceus, Climacogr. 

 p a rvus and Dicranpgr. n i c h o 1 s o n i var. diapason. 



Remarks. Dr Gurley has suggested in the original description that this 

 is one of a group of species as yet undescribed and differing in size, length 

 and angle of divergence of the branches. From our larger collection it 

 appears that this species is very well distinguished from all of its associates 

 by its twisted, uniformly slender branches ; and further that within the spe- 

 cies no differences sufficient for varietal distinctions can be established. 

 Lapworth has compared this species to his D. patulosus and Gurley 

 to D. forchammeri. The large Glenmont specimens indicate that 

 the habit of the rhabdosomes resembled that of D. caduceus Lapw., but 

 that the spiral was much looser and wider. From all three mentioned spe- 

 cies it differs by the smaller width of its branches and from the last two 

 still specially by the less introverted apertural part of the thecae. From 

 the flaccid variety of D . divaricatus ( D . d i v a r i c a t u s var. 

 bicurvatus ) which it resembles in the curvature of its proximal parts it 

 can be distinguished by the slower growth and smaller final width of the 

 branches and the different form of the thecae ; the latter variety having 

 straighter ventral walls. 



